Leishmania donovani

Histoplasma capsulatum. Fungal cells in macrophage of bone marrow smear (Giemsa's stain, oil immersion). Cells of H. capsulatum var capsulatum present in reticuloendothelial cells often can be confused morphologically with the amastigote stages of Leishmania species or Trypanosoma cruzi. Although these cells are 2 to 4 µm long, they lack a kinetoplast and the cytoplasm of the cells is retracted from the poorly staining cell wall, which produces a "halolike" effect around the cells. In this case, the organisms were initially thought to represent L. donovani infection, but careful observation of their morphology led to the correct diagnosis of disseminated histoplasmosis.